Patch from Lorenzo for better handling of non-normalized bignums.
Patch from Lorenzo for better handling of non-normalized bignums.

holmescn/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,holmescn/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme